This invention relates to a method of identifying piston rings having an asymmetrical cross section such as taper face rings, scraper rings or bevelled edged rings. The method comprises the application of a marking which extends from an annular face (flank face) of the piston ring to a circumferential face thereof.
For identifying piston rings, particularly piston rings having a non-cylindrical running face, so-called "top" markings have been stamped on the annular faces of the piston ring adjacent the piston ring gap to ensure a proper positioning of the piston ring when installed in the engine. While the piston rings have the "top" marking on that annular face which is to be oriented towards the combustion chamber, it occurs quite frequently that individual rings, in the course of further machining, stacking or packaging are accidentally inverted so they are positioned in an inverted state in the piston ring stack. Since in general the piston rings are no longer drawn onto the piston manually (this operation has largely been taken over by machines) the installer has to rely fully on the piston ring manufacturer concerning the correct positioning of the piston rings in the packages. Piston rings drawn onto the piston in an inverted position not only affect adversely the operation of the engine, but later necessitate a time-consuming disassembly thereof. Although with significant labor and thus with the substantial cost the above-descirbed error can conceivably be detected during the final inspection of the piston rings, such individual checking is otherwise only seldom justified and furthermore, the possibility of oversight by the inspectors (due to carelessness or fatigue) cannot be discounted.
German Pat. No. 1,251,114 discloses piston rings having a circumferential groove which is provided in the running face of the piston ring for mechanically sensing the position of the piston rings. This type of marking, however, is expensive to provide: markings on the running faces of the piston rings must not exceed a certain thickness since the surface quality of the running faces has to meet very high standards. If a marking of substantial depth is provided, its sealing function in the engine may be adversely affected.
Further, according to German Utility Model (Gebrauchsmuster) No. 7,039,835, each piston ring is provided with a notch which extends from one of the annular faces to one of the circumferential faces of the piston ring. It is a disadvantage of such an arrangement that the notch can only extend into the inner, and not into the outer circumferential face and thus the packaged rings can be checked only with difficulty concerning their correct positioning. If such a notch extended from one of the annular faces to the outer circumferential face (that is, the running face of the piston ring), the latter would no longer have the required sealing properties.
It is further generally known to identify piston rings by stamping the annular faces. Such a method, however, is generally not acceptable because of the resulting protrusions of material and the damaging of the wear-resistant layers which are at least partially applied to the running faces.